Phenolics adhesive shear strength

Bonding, contact angle, heat-treated wood, penetration, phenol-formaldehyde adhesive, shear strength... 

Epoxy-phenolic Epoxy-phenolic adhesives are generally used in aerospace applications requiring high shear strength at temperatures in excess of 150°C. Usually die phenolics are a resole-type, and often the epoxy is a minor component. These adhesives are relatively brittle and have low peel and impact strengths. 

FIGURE 7.1 The effect of temperature on the tensile shear strength of modified epoxy-phenolic compared to other hybrid adhesives (substrate is aluminum).4... 

Not only is low tensile shear strength noticed on moisture aging, but also the mode of failure changes from one of cohesion to adhesion. Table 7.6 shows the effect of humidity and water immersion on an epoxy-nylon adhesive compared to a nitrile-phenolic adhesive. Substrate primers have been used with epoxy-nylon adhesives to provide improved moisture... 

TABLE 7.6 Effect of Humidity and Water Immersion on the Tensile Shear Strength of Epoxy-Nylon and Nitrile-Phenolic Adhesives 10... 

The degree of tensile strength improvement is often in the 50 to 100 percent range. The effect of various fillers and loading ratios on the strength properties of epoxy adhesive formulation is indicated in Fig. 9.9. The effect of different fillers loaded at a constant 100 pph is indicated in Table 9.12 for shear strength on phenolic laminate and aluminum substrates. 

Fillers were found to significantly increase the room temperature tensile shear strength of BTDA cured epoxy adhesives. However, other modifiers such as phenolic or nylon resin did not significantly improve the peel strength, flexibility, or temperature resistance of the unmodified formulation. 

Epoxy and nitrile-phenolic adhesives have been used to bond polyolefin plastics after plasma surface preparation. Shear strengths in excess of 3000 psi have been reported on... 

Various adhesives can be used to bond polyphenylene oxide to itself or to other substrates. Parts must be prepared by sanding or by chromic acid etching at elevated temperature. Methyl alcohol is a suitable solvent for surface cleaning. The prime adhesive candidates are epoxies, modified epoxies, nitrile phenolics, and polyurethanes. Epoxy adhesive will provide tensile shear strength on abraded polyphenylene oxide substrates of 600 to 1300 psi and 1300 to 2200 psi on etched (chromic acid) substrates.71... 

A few preliminary resols have also been made with a 50% replacement of phenol by the P/N fraction of the wood oil. Tests have shown these adhesives to have shear strengths and wood failure comparable to that obtained with Borden s Cascophen 313. This work is in progress. 

An emulsion polymer-isocyanate adhesive, a crosslinked polyvinyl acetate adhesive, a resorcinol-formaldehyde adhesive, a phenol-resorcinol-formalde-hyde adhesive, and an acid-catalyzed phenolic-formaldehyde adhesive developed bonds of high shear strength and wood failure at all levels of acetylation in the dry condition. A neoprene contact bond adhesive and a moisture-curing polyurethane hot-melt adhesive performed as well on acetylated wood as untreated wood in tests of dry strength. Only a cold-setting resorcinol-formal-... 

The objective of this research was to determine whether the degree of heat treatment of the wood influenced the bonding of treated wood with phenol-formaldehyde adhesive. The shear strength of the adhesive bond, the percentage of... 

Spruce (Picea abies Karst) lamellas were used to investigate the influence of the heat treatment of wood on the shear strength of the phenol-formaldehyde adhesive bond. Lamellas were heat treated at two temperatures 180°C and 220°C. The process of heat treatment in a vacuum, developed by Rep and co-workers [36], was used. Prior to heat treatment, all lamellas were planed to dimensions of 350 mm x 100 mm X 18 mm, and oven dried at 103°C. The treatment was performed in a vacuum chamber (Kambic, Laboratory Equipment d.o.o., Semic, Slovenia), where an absolute pressure of 5 kPa was achieved. The lamellas were heated to the desired temperatures, which took about 1 h, and then treated for 3 h at a constant temperature. The lamellas were then left to slowly cool down to room temperature. The lamellas were oven dried before and after heat treatment to determine mass loss. Mass loss (ML) after heat treatment was estimated according to the formula ... 

Table 3.5. Effect of pretreatment on lap shear strength of steel polyvinyl-formal-phenolic adhesive joints... 

The normal service temperatures of these adhesives range from -57°C to 93 °C. Because of their high resistance to creep and most severe environments, neoprene-phenolic joints can withstand prolonged stress. Fatigue and impact strengths are excellent. However, shear strength is lower than that of other modified phenolic adhesives. 

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